SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '912a7320e63a086d99b40dfb23477bf918f8a367b0219fe9c64df4093274d607' 
  AND token = 'rQOkdZi1MGRzCSBeApX8QdvSMRCvViBgzmqr++7kFR4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}